U.S. Rep. John Dingell was scheduled to undergo what his staff described as a "minimally invasive procedure" at Henry Ford Hospital in Detroit on Thursday.

Dingell before delivering his annual "State of the District" speech in Ann Arbor on Monday afternoon.Ryan Stanton | The Ann Arbor News

"He recently developed atrial fibrillation, and the procedure will seek to find the source of the abnormal heart rhythm and correct it," his office said in a statement shared with the media. "He is expected to stay in the hospital overnight and be released Friday."

No other information was immediately available.

Atrial fibrillation, or AF, is the most common type of arrhythmia, a problem with the rate or rhythm of the heartbeat, according to the National Institutes of Health.

"In AF, blood pools in the atria," the NIH website states. "It isn't pumped completely into the heart's two lower chambers, called the ventricles. As a result, the heart's upper and lower chambers don't work together as they should."

People who have AF might not feel symptoms, but it can increase the risk of stroke or cause chest pain or heart failure, according to the NIH.

Dingell, D-Dearborn, announced recently he'll be retiring from Congress at the end of his current term. At the age of 87, he has served in Congress continuously since 1955, making him the longest-serving congressman in U.S. history.

He was in good spirits when he appeared in Ann Arbor earlier this week to deliver his annual "State of the District" speech before a crowd of about 130 community leaders and business professionals at the Kensington Court Hotel.

At one point during his speech, he made light of the fact that he's physically slowing down in his old age, joking that when he bends over to tie his shoes now, he always looks around to see what else he can do while he's down there.

He said he was looking forward to coming home to the district and spending more time with the people he knows and loves.